Manufacture of oxide cathodes



Patented July 16; 192 9.

KAREL MARINUS VAN GESSEL, or EINDHOYEN, NETHERLANDS, ASSIGNOR roaamoconronarron or mnnroa, A manurac'ruan or v No Drawing. Application filed April 6, 1927, Serial Oxide cathodes are manufactured by first oxidizing superficially a core of a highly refractorymetal which does not easily form an alloy with any of the alkaline earth metals such, for example, as tungsten, or molybdenum and then contacting this surface with one or more of the alkaline earth metals, which subsequently are converted into their oxides.

Although asa rule this method gives .excellent results, yet a perfectly uniform distribution of the alkaline earth metal over the. previously oxidized core surface is not ensured under all circumstances.

An improvement of this process is obtained by not superficially oxidizing the above-mentioned core of highly refractory metal itself but by first coating the said core with a film of a readily oxidized metal having a comparatively low pointof volatilization, oxidizing said film partially or entirely and subsequently coating the oxidized film with one or more of the alkaline earth metals. This coating is then heated to such a temperature that the metal of the film gives up its oxygen to the alkaline earth metal and-the metal of the film volatilizes. The alkaline earth metal is thereby converted into an oxide. i

30 The-core which, for "example, may be of tungsten or molybdenum may be coated, for. example, witha film of copper, which subsequently is converted, partially or entirely, into copper oxide. The alkaline earth metal is applied in a metallic state to the surface thus obtained. This may be effected in any manner known for this purpose, for example, by vapourizing barium and precipitating it on the core surface. On heating, 'an exchange of oxygen ensues between the copper and the barium, for which purpose additional supplementary oxygen or air may be applied, if desired, in order to oxidize the barium.

Y The reduced copper'is removed by volatilization.

'It is not unlikely that during a certain part of the process the barium forms with I the copper a kind of alloy and that this is I the reason of the uniformity with'whic'h the 50 barium is automatically distributed over the core surface.

What I claim is: -1. A process of manufacturing oxide cath- CORPORATION or DELAWARE.

oxnm GATHODES.

No. 181,619, and. in the Netherlands April 6, 1926.

odes, comprising coating a core of a refractory metal or metal alloy which does not readily form an alloy'with any of the alkaline earth metals, with a film of a readily oxidized metal haying a comparatively low point of vola- I tlhzatlon, oxidizing partially or entirely the sa1d film, coating the-oxidized film with one or'more of the alkaline earth metals, and then heatlng to such a temperature that the al kalme earth metal is converted into oxide. and the metal of the film is volatilized.

2. A process of manufacturing oxide cathodes, comprising coating a core of a refractory metal or metal alloy which does not readily form an alloy with any of the alkaline earth metals, with a film of a readily oxidized metal having a comparatively low point of '70 volatilization, oxidizing partially or entirely the said film, coating the oxidized film with one or more of the alkaline earth metals by bringing the said film into contact with the vapour of one or more of the alkaline earth metals and precipitating the alkaline earth metal on the film, and then heating to such a temperature that the alkaline earth metal is i converted into oxide and the metal of. the film is volatilized. Q

The process of manufacturing oxide cathodes comprising coating a core of refractory metalor metal alloy with a film of a readily oxidized metal having a comparative-- ly low point of volatilization, oxidizing the 5 said'film, coating the oxidized film with an alkaline earth metal, and then heating the coated core to such a temperature that the alkaline earth metal is converted into oxide,

and theoxid'e film is reconverted into metal 1 which then volatilizes.

4. The process of manufacturing oxide cathodes comprising coating a core of tungsten with a film of copper, oxidizing the said film of copper, coating the oxidized film with barium, and then heating the product to such a temperature that the barium is converted into bariumoxide and the copper oxide film is converted into copper which then v latilizes.

5. The process of manufacturing oxide cathodes which consists in coating a core of a metallic refractory substance which does not readily form an alloy with any of the alkaline earth metals, with a film of a readily oxidized metal, as copper, having a comparatively low point of volatilization, oxidizing the copper,

coating the oxidized copper with an alkaline earth metal, and then heating the product to such a temperature that the alkaline earth metal is converted into anoxide, and the copverted into the oxide and the metal of the film is volatilizedr 7 The process of manufacturmg oxide cathodes comprising coatmg the core of a refractory metal with a film of a readily oxidizcd metal having a comparatively low point of volatilization, oxidizing the said film, coating the oxidized film with bariu1n,'and then heating the coated core to such a temperature that the barium is converted into the oxide, and the metal of the film is volatilized.

KAREL MARINUS VAN GESSEL. 

